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Discussion Starter · #1 ·
Hi, and thanks in advance for your thoughts. I’m new in this group and bought an 81’ GL500 Silverwing Interstate, showing 54K on the odometer, a week ago. I’ve also read many threads here and often performance “issues” come back to carburetion.

This bike probably sat for at least 2 years as the last endorsement on the tag is from 2008. However, I was able to get it started and drive it 10 miles home running mostly or perhaps entirely on the left cylinder. It would rev up to 8k slowly and get on down the road. Once home I found that only the left bank was firing.

I pulled the carbs and cleaned and put it all back together now it fires on both. Now here is the funny part - now I can only get it up to about 5k on the tack. It runs fine up to there but just won’t make enough power to do anything above about 5k. Well in 2nd gear I can get it up to about 6K but it’s not working so hard.

I’ve check the timing and it is spot on. I checked the fuel petcock via pulling a vacuum and running about a gallon of gas out into a can and that looked great. (Had already put in fresh gas)

Compression is 140 on left side and 130 on right so that is fine I think. I have not checked the valve timing yet but I’m guessing it too will be spot-on. I have my curiosity about the power of the spark while it’s not as big as I’d like to see it is blue.

Since this is a GL Interstate I believe it does not have the issues of the ignition that the CX has sometimes above 5k. (I’ve read something about the “white wire” fix”)

So I’m thinking most of you will say to take a closer look at the carbs. With my past bikes most of my carb issues would be at Idle and not on the high-speed side. However, those carbs were not of the CV type.

Also, I’ve checked output to the battery while running and it’s right a 14 volts. The bike rides around fine and I’ve put about 150 miles on it but it’s not ready for the highway as I’m limited to about 55 mph.

Any thoughts about spark at the plugs? I might be back to the Carbs which I thought I did a good job of at the time.

Thanks, Mike
 

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Hi Mike,

some guesses and suggestions

clogged air filter?

dont trust your eyes

try running without one to see if theres any difference



look up the hole in the plug cap where the plug goes

if you see a slot, unscrew the brass tube and remove the gubbins.

If you get a load of black dust instead of a spring, resistor and alloy slug, you need new ones

get non resistor types.



check/clean all electrical connections and grounding
 

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Back to the carbs or that area anyhow. It is easy to get the jets (or maybe just one side), installed in the wrong towers. The larger number jet goes in the brass hex fitting. If they are reversed, you will experience these exact symptoms. Ask me how I know.



Another area will be the boots that attach to the carbs. And the O ring at the head. These carbs like everything right and tight. You can spray some carb cleaner or starting fluid around these areas with the bike running and see if the idle speed changes. A vacuum leak will cause the bike to speed up.



I assume that you checked the float levels while you had the carbs off. They need to be a 15.5 mm. A quick check would be to attach a clear tube to the carb bowl overflow and route it up beside the float bowl. Open the carb drain and see what level the fuel rises in the tube. It should come to just below the seam of the bowl and the body.



I'm betting on the jets being swapped.
 

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Discussion Starter · #4 ·
Reg and Blue Fox,

Thanks for the info. I had previously tried running with no air filter but no change so it went right back in. I took your advice and pulled the resistor caps apart and they looked fine, however if you have a good suggestion on where to get non-resistor caps I will buy them as I’ll never put a radio in. I still need to clean all the electrical connections. I’m getting blue spark but it looks a bit thin. Perhaps I’ll take one of the plugs to my car and see how the spark looks there.



Blue Fox, I had read one of your previous posts on Friday regarding the jets being in the wrong hole – I was betting on that one too and took the bottom off (the carb without the boost pump)on Saturday but the jets were in the correct places. (I did not check the carb with the accelerator pump but looks like I may now) I then sprayed carb cleaner around the manifold at the head – no change. I did use some high-temp non-hardening silicone there when I put them on. Yep, I checked the floats when I assembled but liked your clear tube test and had the tube on hand and that too checked well. Very cool test, I really like that one.

So it looks like my next step is to clean all electrical contacts to the coils and then if problem still persist I will study up on the carbs some more and give it another go.

Thanks,

Mike
 

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Hi, Mike. It sounds like you know what you are doing with your bike. It's hard sometimes to determine how much experience some members have. But I can tell from your posts that you are not a newbie to bikes.



Thats all well and good, but doesn't solve your problem. If the other jet checks out, I'm not sure witch way to point you. You may replace the plug wires. They are cheap and easy to do. Get a solid core plug wire from the auto parts store and screw the wire into the coils and plug cap. The GL ignition is usually very trouble free, so the only other area might be the spark advance unit not operating properly. I'm not sure of the check on that off the top of my head, maybe someone will chime in on that. Or it is probably in the service manual on the drop i/o site.



It sure sounds electrical, but I would still add some Seafoam to my tank to help keep the carbs clean.
 

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Discussion Starter · #6 ·
Blue Fox,

Thanks for the info. I’ll buy a couple of solid core auto plug wires with caps as a test if that helps I can cut a length and use to attach to the original plug caps. I checked the spark advance with a timing light and it’s good. I’ll figure this thing out it will be a process of elimination. Might well be the carbs.



These GL Interstates feel like a good bike not to heavy but has the wind protection, comfortable seating position, and some storage which is very handy. They turn very tight in a parking lot too.



What I don’t know yet is what type of Hiway speeds are reasonable for this 500. What do you typically do for interstate driving? Most of the time I prefer the less traveled back Hiways but if on the Interstate around here we need about 75 mph or better. The weather is just starting to get nice for riding here in Florida. (Seafoam is in the tank!)



Come to think of it the last bike I bought was a 71' Norton Commando which has a positive ground which the previous owner did not understand. When I grounded the bike correctly everything got better. I think I'll also do as Reg suggested and check connections. Seem like the ground goes straight to the starter so perhaps the rest of the bike is grounded through the motor to the frame. Just thinking here.



Mike
 

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hi mike,i cant think of much more to add that the guys above,and you have not already covered.

there is an important green earth under the seat,ensure a good ground here.

and,possibly the coils/leads are breaking down under heat.



are the plugs new,and what colour are they showing
 

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Mike, I would be trying to find at least one spare ignition coil (GL only)and perhaps also an ignition box ( they come off various Hondas - NEC and OKI - you only need to get the right lead length - most have the same pin-out in the correct connector).

Although the ignition box has a very good reliability rating, it may be shutting down at higher pulse rates.

If you have the cover off the ignition trigger coils again, check the gap between the coil's pole piece and the rib on the rotating hub - should be at least 20 thou where it passes EACH pole-piece. The book says 18 to 26 thou.
 

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Mike

NO idea what the problem is but remembered that

sometimes its the simplest things that catch us out

So I suggest you check the cables and watch the link shafts on the carbs

to see that the choke goes fully open when the knob is pushed in and

when the you twist the throttle the shaft turns a full 90 degrees.

It probably isnt that but at least you will have checked it



If you whip the carbs off, I'd stick my finger in the back and check the pistons

can be fully lifted easily and they just as easily plop back down again.

Sticky pistons can stop you getting full power.



AS Don mentioned igntion its probably worth disconnecting the 4 way plug from the

rear case and measuring the resistance of each same coloured pair

yellow/yellow, blue/blue.

these carry the signals from the ignition pulsers

You want to see about 530 ohms between any pair and very high (Megaohms)

resistance between any wire and ground.



As had already been mentioned, ensure you have good ground connections

you can get odd behavoiur on a TI bike with bad/poor grounding.
 

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Discussion Starter · #11 ·
I’ve checked and cleaned the two green wire grounds and added solid core wire from the coils to the resistor plug caps. Then put some mid grade gas and Sea Foam in the tank and went for a 30 mile ride. This time I got the bike up to 65mph which is up about 8mph from last ride.

Both plugs are new and just pulled them – they are bone white. The jets are what the book calls for. I better double check the plugs heat range they are champion RA8HC gapped at .28”



They main fuse is new as the previous owner bought a much needed starter solenoid but did not know how to put it in. (I had to use the screwdriver trick to start and drive it home from the seller) I installed it so it has a brand new main fuse.



Although the plugs are bone white the spark still seams weak looking. I pulled plugs one at a time and started the bike in my darkened garage to watch the plugs. (It runs fine for this on one cylinder - and both sides will do it) The spark is blue but does not come straight down from the center of the electrode – the spark dances around the edges of the round electrode down to the L shaped member. This just seems a bit weird to me.

Well I still have some things to check but before I take the carbs back off I’d like to buy new rubber caps for the middle jet plug, o-rings for the idle screw, and o-rings for the manifolds. Can anyone tell me a good vender for these parts? I also want to get a master cylinder rebuild kit, and new oil filter.



The carb slides worked great and moved freely when I checked. I'm not quite clear on the vacum circuit that must pull them up but will read-up on it before I pull them again.



Thanks,

Mike
 

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Although I've had my GL500 for 126,000 miles, I stick to things like oil changes, tire and brake changes, bulb changes, and tune-ups. Electrical problems usually send me to the (fantastic) forum (where I currently have a post for turn signals that don't flash). For what it's worth, I hadn't used my bike for several months one winter (stored with a full tank of gas and Stabil). When I syatyed using it again, I had a similar problem at high RPMs. Mine was solved with two bottles of fuel and engine cleaner. Pretty lame advice, but as Blue Fox said, sometimes it's the little things that get us! Good luck!
 

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Discussion Starter · #13 ·
Eagle1,



This 500 group is a great bunch. I think I’ll take your advice and just ride it around for awhile on roads that 5k on the tack is fine and burn some Sea-Foam. Maybe the bike is talking to me and telling me to change the rear-end grease, radiator coolant, and unstick the back brake before worrying about top end power. (I’ve been using the front brake only as the back sticks when used. It’s not the external linage so I probably need to take the brake drum apart and clean it)



Cheers, Mike
 

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Discussion Starter · #16 ·
I've put another couple hundred miles on the bike and still all good up to 5K on the tack and the throttle is barley cracked open - there is plenty more but I just get an "air-drone" type noise change at wide open and no more power. I'm sure this noise change is from the butter-fly valves being fully open. The slides are free but I don't have any real way to see if they are moving up - I'm wondering about the air shut off valve?



The cables are fine and I am getting wide open on the butter-flees. Choke is working as intended too.

The jets did check out to be in the right places. Maybe I just missed something in the carb cleaning. I'll study up and clean them again before reinstalling. The fuel pet-cock checked good and a Ferrari mechanic friend looked at the spark with me and thought it was fine.



Well it's off to clean the carbs again.



Mike
 

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Mike, it is getting to be a tougher problem than normal. Can you rev and hold the RPM's up past 6000 in neutral? Not for a long time, but at least for several seconds to test that the electrical system is capable of high revs.



There is a way to test for vacuum piston rise by applying vacuum to the area above the venturi on the engine side. I have not tried this, so the exact procedure is somewhat unknown to me. I have heard of using a small vacuum cleaner and covering the venturi, but not the curved slots above, and applying the end of the hose to that. See if the pistons rise. Problem is, how much vacuum is needed? A vacuum cleaner may be provide more than the engine would and cause them to rise, when the engine would not.



You would probably have caught if the vacuum needles were rigid, and not able to float a bit. Also if the sleeve that the jet needle enters in the bottom of the venturi was missing, you will have problems. These can easily fall out of the body on disassembly and may have rolled off somewhere.
 

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If it were me I would try pulling the plug wires off one at a time while I was riding it when it goes into the drone mode,,see if it acts any different from one side to the other. If the bike completly dies with either one of the wires off, chances are the problem is on the other side.

This may not help diagnose the problem but then again it might ,,can't hurt to try.
 

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Discussion Starter · #19 ·
Blue Fox,



Yep, out of gear - it will rev and hold at 8K - and did not fly apart. Just put the carbs back in for the 3rd time and I don't think it's the carbs anymore.



Now I'm reaching - I've noticed the wire mess type thing in the air box looks fairly old and clogged up. I can see that air will flow under it to the carbs but am thinking about taking it out. I also had a car in the mid 80's that someone ran leaded gas in and that clogged the catalectic converter, a test pipe to replace the converter fixed it right up. It does not seem that the pipes are clogged but I'm just thinking here.









Mike
 

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Discussion Starter · #20 ·
Allen,





The left side is stonger than the right running one at a time. Hmmm.....







Mike
 
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